1. Field of the Invention
The present invention relates to an apparatus for and a method of testing a pad conditioner of a chemical mechanical polishing (CMP) apparatus.
2. Description of the Related Art
Today's semiconductor devices have densely integrated multi-layered structures. Therefore, it is essential for the manufacturing of a semiconductor device to include a polishing process for planarizing layers formed on a semiconductor wafer. The polishing process typically employs CMP (chemical mechanical polishing). Moreover, CMP can produce excellent flatness over a wide region as well as a narrow region. Therefore, the current trend is to use CMP as the process for polishing large-diameter wafers.
More specifically, in the CMP process, a tungsten or oxide layer on a wafer is polished simultaneously by mechanical friction and by a chemical reaction. The mechanical polishing is effected by holding the wafer with suction to a polishing head, bringing the wafer into contact with a polishing pad, and rotating the polishing head so that the surface of the wafer is polished by friction between the polishing pad and the surface of the wafer. The chemical polishing is effected by supplying a chemical slurry between the polishing pad and the wafer.
In addition, the condition of the surface of the polishing pad of the CMP apparatus is an important factor affecting such characteristics as the uniformity and flatness of the polished surface of a wafer. Therefore, the condition of the surface of the polishing pad must be maintained in its initial state if the planarization process is to be most effective. However, the polishing pad may be damaged due to abrasives or foreign substances becoming jammed between the polishing pad and the wafer during the polishing process. In this case, the surface of the polishing pad deteriorates such that the efficacy of the planarization process is reduced.
Therefore, various kinds of pad conditioners and methods of using the pad conditioners to maintain the surface condition of the polishing pad have been proposed. The pad conditioners include a circular plate formed of an alloy of nickel and iron, and diamond particles attached to the circular plate. A generally known pad conditioning method is to entirely and uniformly abrade the surface of the polishing pad by scrubbing it with the pad conditioner.
FIG. 1 illustrates an example of a conventional CMP apparatus. The conventional CMP apparatus 20 includes a polishing table (not shown) that rotates at a predetermined number of rpm's, a polishing pad 23 mounted on the upper surface of the polishing table for polishing a wafer 10, a polishing head 25 for holding the wafer 10 against the polishing pad 23, a pad conditioner 29 pivotably supported at one side of the polishing pad 23 and operative to score the polishing pad 23 such that the initial surface roughness of the polishing pad 23 is maintained, and a slurry supplier 27 for supplying an abrasive slurry onto the polishing pad 23. The polishing head 25 picks up a wafer 10 using suction. Then the polishing head 25 places the wafer against the polishing pad 23. The polishing pad 23 is rotated and slurry is dispensed onto the polishing pad by slurry supplier 27. The entire surface of the wafer 10 is thus uniformly polished by mechanical friction from contact with the polishing pad 23 and by a chemical reaction with the slurry.
FIG. 2 illustrates a conventional pad conditioner of a CMP apparatus. The conventional pad conditioner 29 includes a conditioner main body 290b and a cover 290a for covering the conditioner main body 290b. The conditioner main body 290b includes a mounting portion 291 by which the pad conditioner is mounted in the CMP apparatus 20, a head portion 294, and an arm portion 293 connecting the mounting portion 291 and the head portion 294.
More specifically, the mounting portion 291 includes a swing motor (not shown) for swinging the head portion 294 and the arm portion 293 about a vertical axis, a rotary motor (not shown) for rotating the head portion 294, a first pulley 292 engaged with the rotary motor, and a gas supply unit (not shown) for selectively providing gas into or withdrawing the gas from a gas supply hole 294a. 
In addition, the head portion 294 of the pad conditioner 29 includes a polishing disk 295a made up of diamond particles that score the polishing pad 23, a conditioner head 295 (hereinafter referred to merely as a “head”) to which the polishing disk 295a is held, a piston 298 fixed to an upper surface of the head 295, a head raising/lowering unit 296 provided with a diaphragm (not shown) for raising and lowering the head 295 and the piston 298 according to the pressure created in the gas supply hole 294a by the gas supply unit, and a second pulley 297 engaged with an upper portion of the head raising/lowering unit 296. The gas supply hole 294a extends through the center of the second pulley 297 so as to be in fluid communication with the diaphragm.
In addition, the arm portion 293 has a timing belt 299 connecting the first pulley 292 and the second pulley 297.
The conventional pad conditioner 29 operates as follows.
When the polishing pad 23 is to be conditioned, an operator turns on the swing motor and the rotary motor together with the gas supply unit to supply gas into the gas supply hole 294a. As a result, the head portion 294 and the arm portion 293 are swung back and forth about the mounting portion 291 by the swing motor, and the head 295 is rotated by the rotary motor via the pulleys 292 and 297 and the belt 299. At the same time, the pressure of the gas supplied by the gas supply unit expands the diaphragm to thereby lower the head 295 into contact with the polishing pad 23. Thus, the polishing pad 23 is scored by the polishing disk 295a. 
Then, when the conditioning operation is to be terminated, the operator turns off the swing motor and the rotary motor and simultaneously operates the gas supply unit to evacuate the gas supply hole 294a. As a result, the head portion 294 stops oscillating, the head 295 stops rotating and, at the same time, the head 295 is raised by the contraction of the diaphragm resulting from the negative pressure (vacuum) created in the gas supply hole 294a. Therefore, the polishing pad 23 and the head 295 are separated from each other. The conditioning operation of the polishing pad 23 is repeated by the operator over the course of one or more polishing processes.
However, the diaphragm of the pad conditioner 29 is made of rubber. Therefore, the diaphragm can fail or develop a leak after a period of extended use of the pad conditioner such that the head 295 can not be smoothly raised and lowered can not be raised and lowered at all.
Thus, the head portion 294 including the diaphragm is periodically disassembled and replaced to avoid such problems. That is, preliminary maintenance (PM) is performed. However, even then the head portion 294 including the diaphragm may operate so roughly that the rate at which material is removed during the CMP process decreases, thereby lowering the efficiency of the CMP process, creating frequent EPD (end point detection) errors, and necessitating more frequent PM.